1. Field of the Invention
The present invention relates to a semicustom semiconductor IC (integrated circuit) device and, in particular, to a signal terminal structure for macro cells employed in the manufacture of a semicustom semiconductor IC Device.
2. Description of the Related Art
A semicustom semiconductor IC device is structured by combining together various kinds of initially prepared macro cells in accordance with a circuit layout, requisite characteristics, etc., as requested by the users. The term "macro cell" generally refers to an IC block prepared as a standard one. The macro cell covers a range from a large block (macro block), such as a ROM section and RAM section, to a block of small circuit size, that is, a primitive block, such as standard cells of which various kinds of logic units are configured.
FIG. 1 shows a block diagram for explaining micro cells for a conventional semicustom semiconductor circuit device and a way how to connect them. A macro cell 10 has signal terminals A to D and a macro cell 12 has signal terminals E to H. The signal terminals A to H are so provided as to correspond to respective signals. Of those signal terminals A to H, those desired signal terminals, such as the terminals A and F, B and H, C and E and D and G as shown in FIG. 1, are connected together by any proper ones of wires 14-1 to 14-4 with the use of an automatic connection technique.
Since the signal terminals in the conventional macro cells are of such a type that each corresponds to a single signal, the associated terminals cannot be connected to each other at the shortest distance at all times from the standpoint of a circuit arrangement. Further, the wires, if being bent at many places, occupy a larger connection area (channel area), thus increasing a resultant chip size.
FIG. 2 is a block diagram for explaining another array of macro cells in a conventional semicustom semiconductor IC device and a way how to connect them. In the embodiment shown in FIG. 2, the pitch X of those adjacent wires in a horizontal direction, as well as the pitch Y of those adjacent wires in a vertical direction, is determined for the connection of the respective signal terminals of the macro cells 10 and 12. The respective signal terminals of the macro cells 10 and 12 are arranged, at the wire pitch X (or the wire pitch Y), around the macro cells 10 and 12. In this case, the arrangement of wires 14-1 to 14-5 in the horizontal and vertical directions is determined in accordance with the wire pitches X and Y, respectively, and those associated ones of the respective terminals A to E and F to J are connected together with the use of the automatic connection technique.
If the automatic connection technique is employed with connection wire pitches initially determined as shown in FIG. 2, resultant wire pitches X and Y usually differ. Changing the wire pitches in the horizontal and vertical directions is due to the difference created between the flatness of a first-level aluminum connection layer and that of a second-level aluminum connection layer which is caused by those stepped areas resulting from, for example, via holes. As a result, the second-level aluminum connection layer has to be made wider than the first-level aluminum connection layer. In FIG. 2, the first- and second-level aluminum connection layers are formed, for example, in the horizontal and vertical directions, respectively.
In the conventional semicustom semiconductor IC device, the signal terminals have their array position determined in accordance with either one of the wire pitch X in the horizontal direction and wire pitch Y in the vertical direction. The macro cell, if being rotated clockwise through an angle of 90.degree. to 270.degree., has its wire terminal position misaligned relative to that of the associated macro cell, failing to achieve a wire connection desired. It is, therefore, possible to simply never make rotation or simply to make a 180.degree. rotation, thus involving less degree of freedom with which the micro cell is laid out.